6.1.3 fixes a security bug that could allow someone with physical access to your iPhone to access the phone app.

This is for iPhone and iPad. You can get the full installer by plugging into iTunes. You can choose to download only and install later. This is recommended so that you can restore the device should you ever have to.

You can also download on the device. This is much faster to download, but if you ever have to restore the device, you'll have to download the updater(s) first.

"Design is not just what it looks like and feels like. Design is how it works."
Steve Jobs